Nozzle for cooling vacuum heat treatment furnace

ABSTRACT

Embodiments of the disclosure are drawn to a system for heat treatment of a mold. The system includes a vacuum heat treatment furnace. The vacuum heat treatment furnace includes a tray for receiving the mold, a plurality of nozzles configured to discharge gas flows and arranged into one or more rows that are evenly distributed around a perimeter of the vacuum heat treatment furnace, and one or more extendible pipes installed on a selection of the nozzles. The extendible pipes are selectively extended to one or more lengths.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of International Application No.PCT/CN2015/078486, filed on May 7, 2015, which claims priority to andbenefits of Chinese Patent Application No. 201410437613.1, filed on Aug.29, 2014. The contents of both of the above-referenced applications areherein incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a vacuum heat treatment system forprocessing a mold, and more particularly relates to a vacuum heattreatment furnace having one or more cooling nozzles.

BACKGROUND

Die casting molds have become more widely used in applications invarious fields in recent years. These applications have promoted thedevelopment of ultra-large die casting molds, and die casting molds withmore complicated shapes and/or deeper cavities, which lead to higherrequirements for the materials and the performance of heat treatment ofthese molds. At present, die casting molds are generally cooled by usinggas-quenching vacuum heat treatment furnace. However, because the moldin the vacuum heat treatment furnace is typically at a distance from thecold gas source when cooling, the gas cannot to be blown to keypositions of the mold directly. For example, almost all of the typicalvacuum heat treatment systems cannot cool some sections of the mold,such as the bottom and/or root of a cavity of the mold, at a fastcooling speed, which may cause these sections of the mold to haveundesirable properties during and/or after the heat treatment. This maycause an initial failure in these sections of the mold during use. Forexample, the bottom and/or root of the cavity of the mold are keypositions for making die casting products, and may affect the appearanceand/or quality of die casting products, which may eventually result inearly discard of the mold because the appearance and/or properties ofthe die casting products cannot meet desired requirements. Therefore,there is a need for systems and methods to improve the heat treatment adie casting mold, particularly the bottom and/or root of the cavity of adie casting mold.

Increasing the cooling speed during quenching may improve the heattreatment of the mold. A potential research direction may includeimproving the heat treatment by increasing the cooling speed of thebottom and/or root of a deep cavity of a die casting mold. Solving thisproblem may greatly improve the heat treatment of die casting moldshaving large and/or deep cavities and thus effectively increase the lifeof these molds. Currently, when a vacuum heat treatment system performsheat treatment on a die casting mold having a deep cavity, the coolingspeed of the bottom and/or root of the deep cavity of a die casting moldis slow. This is because the gas ejected from a nozzle of the vacuumheat treatment system is at a distance from the mold during cooling,which may reduce the cooling speed and affects the heat treatment of themold, particularly of the bottom and/or root of the deep cavity of themold. Moreover, the mold may have various shapes, such as recess molds,convex molds, and steps. The distances from the nozzle to differentpositions of the cavity of a recess mold or the root of a convex moldvary, which can cause the cooling speed of different positions of themold to be uneven. This may cause heterogeneous properties of heattreatment at different positions of the die casting mold, which may evenincrease the risk of large deformation and cracking of the mold.

As described above, the undesirable heat treatment properties of a diecasting mold having a cavity, e.g., a deep cavity, can be caused byuneven cooling speeds at various positions of the mold, e.g., at thebottom and/or root of the cavity. One major cause is that the cold gassource is at a longer distance away from the deep cavity of the diecasting. Thus, there is a need for systems and methods to decrease thedistance between the cavity and the cold gas source so as to increasethe cooling speed of the cavity of the mold.

SUMMARY

Embodiments of the present disclosure are directed to methods,apparatus, and systems for cooling a mold. Various embodiments of thedisclosure may include one or more of the following aspects.

One aspect of the present disclosure involves a system for processing adie casting mold. The system may include a vacuum heat treatment furnacecomprising: a plurality of nozzles, and one or more extendible pipes,and one or more thermocouples. The die casting mold may include a deepcavity. The plurality of nozzles may be arranged into one or more rowsthat are evenly distributed around a perimeter of the vacuum heattreatment furnace. A selection of the plurality of nozzles may beinstalled with the extendible pipe. The length of the extendible pipemay range from 50 mm to 250 mm, and may be adjustable in accordance witha depth of the deep cavity of the die casting mold so that a distancebetween an open end of the extendible pipe and the interior surface ofthe cavity may range from 450 mm to 600 mm. The vacuum heat treatmentfurnace may further include a tray located at a central position insidethe vacuum heating furnace, and the die casting mold may be received onthe tray. The thermocouples may be placed on the surface of the deepcavity. The extendible pipe may be made of a graphite-based material,and may have a cylindrical tubular shape, which has a circular interiorperimeter. The interior of a front half portion of the extendible pipemay have a circular stepped shape, and may be installed onto the openend of one of the nozzles. An exterior wall of a rear portion of theextendible pipe may include a plurality of screw holes for fixing theextendible pipe by fastening bolts or screws through the screw holes.

Another aspect of the present disclosure involves a system for heattreatment of a mold. The system may include a vacuum heat treatmentfurnace. The vacuum heat treatment furnace may include a tray forreceiving the mold, a plurality of nozzles configured to discharge gasflows and arranged into one or more rows that are evenly distributedaround a perimeter of the vacuum heat treatment furnace, and one or moreextendible pipes installed on a selection of the nozzles. The extendiblepipes may be selectively extended to one or more lengths. The mold maybe a die casting mold comprising a cavity. The system may furtherinclude one or more thermocouples placed on the interior surface of thecavity. The lengths of the extendible pipes may range from 50 mm to 250mm, such that a distance between an open end of at least one of theextendible pipes and the surface of the mold may range from 450 mm to600 mm, and/or that a distance between an open end of at least one ofthe extendible pipes and the interior surface of the cavity may rangefrom 450 mm to 600 mm. The extendible pipes may be selectively extendedto lengths such that distances between open ends of the extendible pipesand the surface of different parts of the mold are substantially thesame. The extendible pipes may be made of at least one graphite-basedmaterial. The extendible pipes may have a shape of a cylindrical tubewith a circular interior perimeter. A front half portion of the interiorof the extendible pipes may have a circular stepped shape and may beconfigured to enclose at least part of one of the nozzles. An exteriorwall of a rear portion of the extendible pipes may include a pluralityof screw holes for fixing the extendible pipes by fastening bolts orscrews through the screw holes.

Another aspect of the present disclosure involves a system for heattreatment of a mold. The method may include receiving the mold in avacuum heat treatment furnace. The vacuum heat treatment furnace mayinclude a tray for receiving the mold, a plurality of nozzles configuredto discharge gas flows and arranged into one or more rows that areevenly distributed around a perimeter of the vacuum heat treatmentfurnace, and one or more extendible pipes installed on a selection ofthe nozzles. The method may further include selectively extending theextendible pipes to one or more lengths, and discharging the gas flowsfrom the plurality of nozzles to cool the mold. The mold may be a diecasting mold comprising a cavity. The method may further includemeasuring at least one temperature on the interior surface of the cavityusing one or more thermocouples placed thereon. The method may furtherinclude extending the extendible pipes to lengths ranging from 50 mm to250 mm. The method may further include extending at least one of theextendible pipes to a length such that the distance between an open endof the extendible pipe and the surface of the mold ranges from 450 mm to600 mm and/or that the distance between an open end of the extendiblepipe and the interior surface of the cavity ranges from 450 mm to 600mm. The method may further include selectively extending the extendiblepipes to lengths such that distances between open ends of the extendiblepipes and the surface of different parts of the mold are substantiallythe same. The method may further include further comprising cooling thedifferent parts of the mold at substantially the same speed.

Additional objects and advantages of the present disclosure will be setforth in part in the following detailed description, and in part will beobvious from the description, or may be learned by practice of thepresent disclosure. The objects and advantages of the present disclosurewill be realized and attained by means of the elements and combinationsparticularly pointed out in the appended claims.

It is to be understood that the present disclosure is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description or illustrated inthe drawings. The present disclosure is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be used as a basis fordesigning other structures, methods, and systems for carrying out theseveral purposes of the present disclosure. It is important, therefore,to recognize that the claims should be regarded as including suchequivalent constructions insofar as they do not depart from the spiritand scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thepresent disclosure, and together with the description, serve to explainthe principles of the disclosure.

FIG. 1 depicts a schematic representation illustrating a cross-sectionalview of an exemplary vacuum heat treatment furnace, according toembodiments of the present disclosure.

FIG. 2 depicts a schematic representation illustrating a side view anexemplary nozzle of the vacuum heat treatment furnace of FIG. 1,according to embodiments of the present disclosure.

FIG. 3 depicts a schematic representation illustrating a left side viewof the nozzle of FIG. 2.

FIG. 4 depicts a schematic representation illustrating a cross-sectionalview of the nozzle of FIG. 2 taken along the line A-A of FIG. 3.

FIG. 5 depicts a schematic representation illustrating a cross-sectionalview of an exemplary vacuum heat treatment furnace, in which anexemplary die casting mold is placed on a tray, according to embodimentsof the present disclosure.

FIG. 6 depicts a schematic representation illustrating a cross-sectionalview of the vacuum heat treatment furnace of FIG. 1 taken along the lineA-A of FIG. 5.

FIG. 7 depicts a schematic representation illustrating a cross-sectionalview of the vacuum heat treatment furnace of FIG. 1 taken along the lineB-B of FIG. 6.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, which areillustrated in the accompanying drawings. Wherever possible, the samereference numbers will be used throughout the drawings to refer to thesame or like parts.

FIG. 1 depicts a schematic representation illustrating a cross-sectionalview of an exemplary vacuum heat treatment system, e.g., a vacuum heattreatment furnace 3. Vacuum heat treatment furnace 3 may have a tubularcylindrical shape. In the exemplary embodiment, vacuum heat treatmentfurnace 3 includes a plurality of nozzles 1. Nozzle 1 may be tubularand/or cylindrical in shape. Nozzles 1 may be arranged into a pluralityof rows, e.g., 12 rows. For example, each row may include 6 nozzles, andvacuum heat treatment furnace 3 may have a total of 72 nozzles. The rowsof nozzles 1 may be evenly distributed around the perimeter of vacuumheat treatment furnace 3, for example, spaced at 30° intervals. As shownin FIG. 1, the positions of twelve rows of nozzles 1 are located at 0°to 330° around the perimeter of a cross-section of vacuum heat treatmentfurnace 3.

Vacuum heat treatment furnace 3 may further include one or moreextendible pipes 2. FIG. 2 depicts a schematic representationillustrating a side view of an exemplary embodiment of nozzle 1. Asshown in FIG. 2, extendible pipe 2 may be installed on nozzle 1.Extendible pipe 2 may be formed from a suitable type of material that issubstantially stable and/or inert at heat-treat temperatures, such asgraphite-based materials or graphite-like materials. Extendible pipe 2may have a generally cylindrical shape. For example, extendible pipe 2may have a cylindrical tube shape. The exterior and/or interiorperimeters of the cylindrical tube may be substantially circular.Extendible pipe 2 may be installed fixedly or removably onto an open endof nozzle 1.

FIG. 3 depicts a schematic representation illustrating a left side viewof nozzle 1 installed with extendible pipe 2 of FIG. 2. FIG. 4 depicts aschematic representation illustrating a cross-sectional view of nozzle 1installed with extendible pipe 2 of FIG. 2 taken along the line A-A ofFIG. 3. As shown in FIGS. 2-4, a front half section of the interior ofextendible pipe 2 may have a circular stepped shape, which may encloseat least part of nozzle 1. An exterior wall of a rear section ofextendible pipe 2 may have a plurality of screw holes 5 for fixingextendible pipe 2 on nozzle 1. For example, a plurality of fasteners maybe used to fix extendible pipe 2 to nozzle 1 and/or the length ofextendible pipe 2 by any suitable fastening means that mechanicallyjoins or affixes nozzle 1 and extendible pipe 2, such as by fasteningscrews 6 through screw holes 5, or fastening bolts 6 through screw holes5 with suitable nuts.

The length of extendible pipe 2 may range from about 50 mm to about 250mm, and may be selected or adjusted in accordance with the shape of adie casting mold, for example, the depth of a deep cavity of the diecasting mold. FIG. 5 depicts a schematic representation illustrating across-sectional view of vacuum heat treatment furnace 3. As shown inFIG. 5, an exemplary die casting mold 4 is placed on a tray in vacuumheat treatment furnace 3 for heat treatment. FIG. 6 depicts a schematicrepresentation illustrating a cross-sectional view of vacuum heattreatment furnace 3 taken along the line A-A of FIG. 5. FIG. 7 depicts aschematic representation illustrating a cross-sectional view of vacuumheat treatment furnace 3 taken along the line B-B of FIG. 6.

As shown in FIGS. 6 and 7, die casting mold 4 may be a recess moldand/or a convex mold. The positions for placing die casting mold 4 invacuum heat treatment furnace 3 can be widely different. Thus, toachieve the desirable properties of heat treatment of die casting mold4, the cooling speed of die casting mold 4 may be accelerated and/or maybecome substantially even at different positions of die casting mold 4,such as the bottom of the deep cavity, by extending nozzles 1 withextendible pipe 2.

As shown in FIGS. 5-7, a selection of nozzles 1 may be extended byselectively adding, installing, or extending extendible pipes 2 to theselected nozzles 1. For example, a number of nozzles 1 at differentpositions around vacuum heat treatment furnace 3 may be selected. Theinstalled or extended extendible pipes 2 may have different lengths ormay be adjusted to different lengths. The selection of nozzles 1 to beextended and/or the lengths of the extendible pipes 2 may be determinedin accordance with the shape and/or installing position of die castingmold 4 in vacuum heat treatment furnace 3, such that the distancesbetween the ends of nozzles 1 and the surfaces of die casting mold 4,including the interior surface of the deep cavity of die casting mold 4,range from about 450 mm to about 600 mm.

As described herein, the open end of nozzle 1 may refer to the end ofnozzle 1 having an opening from which cooling gas is ejected, or theopen end of extendible pipe 2 installed on nozzle 1 from which coolinggas is ejected. Similarly, the open end of extendible pipe 2 may referto the end of extendible pipe 2 having an opening from which gas coolinggas is ejected. Therefore, the uneven cooling or the heterogeneouscooling speeds of different parts of die casting mold 4 caused by thedifferent distances between the ends of nozzles 1 and the surface of thedifferent parts of die casting mold 4, such as the deep cavity, isreduced.

Die casting mold 4 may be any type of mold to be heat treated. In someembodiments, the distance between the end of extendible pipe 2 and thesurface of die casting mold 4, such as the interior surface of thecavity of die casting mold 4, is adjusted to be between about 450 andabout 600 mm by adjusting, e.g., extending or retracting, the length ofextendible pipe 2. In such situations, the evenness of cooling and/orthe cooling speed of die casting mold 4 may be desirably controlled.

In some embodiments, a method for cooling die casting mold 4 in vacuumheat treatment furnace 3 may include one or more of the following steps.Step 1 may including placing die casting mold 4 on a tray provided invacuum heat treatment furnace 3. Die casting mold 4 may have a deepcavity, and may be placed on the tray and located at a central positionin vacuum heat treatment furnace 3. In some embodiments, one or morethermocouples 7, e.g., about 9 thermocouples, may be placed on thesurface of the deep cavity of die casting mold 4 to measure thetemperatures of the surface during cooling. Step 2 may includeinstalling or extending extendible pipes 2 to a selection of nozzles 1.Step 2 may further include selectively adjusting the lengths ofextendible pipes 2 such that the ends of nozzles 1 and/or extendiblepipes 2 may have similar distances to the surfaces of different parts ofdie casting mold 4. Step 3 may include discharging cold gas flowsthrough the ends of a selection of nozzles 1 and/or extendible pipes 2during cooling of die casting mold 4. The cold gas flow may be directlydischarged to the surface of die casting mold 4, including the interiorsurface of the deep cavity of die casting mold 4. The cold gas flowsthen carry amounts of heat away from die casting mold 4. Step 4 mayinclude passing the heated gas flows through a heat exchanger. Step 4may further include discharging cold gas flows again from the ends ofnozzles 1 and/or extendible pipes 2. Steps 1 to 4 may be iterated for asuitable number of times so as to achieve cooling or fast cooling of thesurface of die casting mold 4, e.g., the surface of the deep cavity ofdie casting mold 4, and/or even cooling of various positions of diecasting mold 4.

EXAMPLE 1 Comparison of Cooling Exemplary Die Casting Molds Having aRecess in an Exemplary Vacuum Heat Treatment Furnace With and WithoutExtendible Pipes 2

Testing data were obtained for cooling two exemplary die casting molds4, both of which had a recess and were heated to be at substantially thesame temperature using the same technology before cooling. The testingdata, i.e., cooling speed (° C./min), are summarized in Table 1 below.

TABLE 1 Comparison of testing data for cooling die casting molds invacuum heat treatment furnace 3 with and without extendible pipes 2. Themold was placed The mold was placed at at the center of the tray, thecenter of the tray, and and extendible pipes one extendible pipe 2 2were not extended was extended by 200 mm Temperature range: Temperaturerange: (1020-540° C.) (1020-540° C.) cooling speed ° C./min coolingspeed ° C./min B2: On the end surface 65.56 90.77 of the opening of therecess B3: The upper portion 29.56 38.77 of the bottom of the recess B4:The middle portion 34.33 57.85 of the bottom of the recess B5: The lowerportion 23.78 40.00 of the bottom of the recess B6: An upper portion48.00 67.08 in the recess 100 mm from the end surface of the opening B7:A middle portion 44.00 62.92 in the recess 100 mm from the end surfaceof the opening B8: A lower portion 43.22 69.69 in the recess 100 mm fromthe end surface of the opening B9: A middle portion 47.33 64.92 in therecess 100 mm from the end surface of the opening

It can be seen from Table 1 above, after an exemplary nozzle 1 locatedat the opening of the recess of one die casting mold 4 was installedwith an exemplary extendible pipe 2, the cooling speed of variouspositions of the recess of die casting mold 4 was increased. Forexample, the cooling speed of the surface of the recess of die castingmode 4 was generally increased by 50 percent. These testing data showthat the cooling speed at the recess of the deep cavity of die castingmold 4 was increased and thus the heat treatment of die casting mold 4was improved. The problem of different cooling speeds of the surface ofthe mold can be solved by installing extendible pipes 2 to a selectionof nozzles 1 at different positions.

It can be seen from above example that the cooling speed of die castingmold 4, e.g., the cooling speed of the surface of the cavity of diecasting mold 4, can be desirably increased by using extendible pipe 2.

The vacuum heat treatment furnace 3 described in the present applicationmay be generally applied to various types of molds. For example, besidesdie casting mold 4 having a recess or a deep cavity as described above,die casting mold 4 whose thickness is not uniform, such as a mold havingsubstantial thickness differences between different portions, can alsobe cooled using vacuum heat treatment furnace 3. For example, one ormore extendible pipes 2 may be used to cool the thicker portions of themold, so as to achieve comparable or similar cooling speed as thethinner portions of the mold. This may reduce the risk of deformationand cracking of the mold and improve the heat treatment performance ofthe material of the mold, such as by obtaining desirable properties ofthe mold after the heat treatment.

Based on the above example and manufacturing practice, the presentdisclosure describe systems and methods that solve the problem ofpartial slow cooling and heterogeneous cooling of any suitable type ofmold during heat treatment, e.g., gas quenching, which may improve theheat treatment performance of the mold and reduce the probability ofcracking during gas quenching, and may extend the life of the mold.

The many features and advantages of the present disclosure are apparentfrom the detailed specification, and thus, it is intended by theappended claims to cover all such features and advantages of the presentdisclosure that fall within the true spirit and scope of the presentdisclosure. Further, since numerous modifications and variations willreadily occur to those skilled in the art, it is not desired to limitthe present disclosure to the exact construction and operationillustrated and described, and accordingly, all suitable modificationsand equivalents may be resorted to, falling within the scope of thepresent disclosure.

Moreover, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be used as a basis fordesigning other structures, methods, and systems for carrying out theseveral purposes of the present disclosure. Accordingly, the claims arenot to be considered as limited by the foregoing description.

What is claimed is:
 1. A system for processing a die casting mold,comprising: a vacuum heat treatment furnace, comprising: a plurality ofnozzles, and one or more extendible pipes, and one or morethermocouples, wherein the die casting mold comprises a deep cavity,wherein the plurality of nozzles are arranged into one or more rows thatare evenly distributed around a perimeter of the vacuum heat treatmentfurnace, wherein a selection of the plurality of nozzles are installedwith the extendible pipe, wherein the length of the extendible piperanges from 50 mm to 250 mm, and is adjustable in accordance with adepth of the deep cavity of the die casting mold so that a distancebetween an open end of the extendible pipe and the interior surface ofthe cavity ranges from 450 mm to 600 mm, wherein the vacuum heattreatment furnace further comprises a tray located at a central positioninside the vacuum heat treatment furnace, and the die casting mold isreceived on the tray, and wherein the thermocouples are placed on thesurface of the deep cavity.
 2. The system of claim 1, wherein theextendible pipe is made of a graphite-based material, and has acylindrical tubular shape, which has a circular interior perimeter,wherein the interior of a front half portion of the extendible pipe hasa circular stepped shape, and is installed onto the open end of one ofthe nozzles, wherein an exterior wall of a rear portion of theextendible pipe comprises a plurality of screw holes for fixing theextendible pipe by fastening bolts or screws through the screw holes. 3.A system for heat treatment of a mold, comprising: a vacuum heattreatment furnace comprising a tray for receiving the mold; a pluralityof nozzles configured to discharge gas flows and arranged into one ormore rows that are evenly distributed around a perimeter of the vacuumheat treatment furnace; and one or more extendible pipes installed on aselection of the nozzles; wherein the extendible pipes are selectivelyextended to one or more lengths.
 4. The system of claim 3, wherein themold is a die casting mold comprising a cavity.
 5. The system of claim4, further comprising one or more thermocouples placed on the interiorsurface of the cavity.
 6. The system of claim 3, wherein the lengths ofthe extendible pipes range from 50 mm to 250 mm.
 7. The system of claim4, wherein a distance between an open end of at least one of theextendible pipes and the surface of the mold ranges from 450 mm to 600mm.
 8. The system of claim 4, wherein a distance between an open end ofat least one of the extendible pipes and the interior surface of thecavity ranges from 450 mm to 600 mm.
 9. The system of claim 4, whereinthe extendible pipes are selectively extended to lengths such thatdistances between open ends of the extendible pipes and the surface ofdifferent parts of the mold are substantially the same.
 10. The systemof claim 3, wherein the extendible pipes are made of at least onegraphite-based material.
 11. The system of claim 3, wherein theextendible pipes have a shape of a cylindrical tube with a circularinterior perimeter.
 12. The system of claim 11, wherein a front halfportion of the interior of the extendible pipes has a circular steppedshape and is configured to enclose at least part of one of the nozzles.13. The system of claim 3, wherein an exterior wall of a rear portion ofthe extendible pipes comprises a plurality of screw holes for fixing theextendible pipes by fastening bolts or screws through the screw holes.14. A method for heat treatment of a mold, comprising: receiving themold in a vacuum heat treatment furnace, the vacuum heat treatmentfurnace comprising: a tray for receiving the mold; a plurality ofnozzles configured to discharge gas flows and arranged into one or morerows that are evenly distributed around a perimeter of the vacuum heattreatment furnace; and one or more extendible pipes installed on aselection of the nozzles; selectively extending the extendible pipes toone or more lengths, and discharging the gas flows from the plurality ofnozzles to cool the mold.
 15. The method of claim 14, wherein the moldis a die casting mold comprising a cavity.
 16. The method of claim 15,further comprising measuring at least one temperature on the interiorsurface of the cavity using one or more thermocouples placed thereon.17. The method of claim 14, further comprising extending the extendiblepipes to lengths ranging from 50 mm to 250 mm.
 18. The method of claim14, further comprising extending at least one of the extendible pipes toa length such that the distance between an open end of the extendiblepipe and the surface of the mold ranges from 450 mm to 600 mm.
 19. Themethod of claim 14, further comprising selectively extending theextendible pipes to lengths such that distances between open ends of theextendible pipes and the surface of different parts of the mold aresubstantially the same.
 20. The method of claim 19, further comprisingcooling different parts of the mold at substantially the same speed.